Radar system, imaging method, and imaging program

ABSTRACT

The radar system 11 comprises a plurality of transmission antennas 12 which irradiate electromagnetic waves, a plurality of receiving antennas 13 which receive the irradiated electromagnetic waves that have been reflected and generating measurement signals, radar signal transmission and receiving means 14 for obtaining the measurement signals, movement estimation means 15 for estimating the movement of an object, and motion-compensated image generation means 16 for generating a radar image based on the measurement signals and the estimated object movement.

TECHNICAL FIELD

The present invention relates to a radar system, an imaging method, andan imaging program for receiving electromagnetic waves reflected by anobject and performing imaging.

BACKGROUND ART

A body scanner system, as illustrated in FIG. 18, has been introduced inairports and the like. In the body scanner system, an electromagneticwave such as a millimeter wave is irradiated to an object (such as ahuman body) 800 that stops within an area 802. A plurality of radars(including a transmission antenna and a receiving antenna) 804 areinstalled on a side panel 803. Electromagnetic waves reflected by theobject 800 are measured, and imaging (imaging) is performed based on themeasurement signals (radar signals) (refer to non-patent literature 1,for example). Based on the images (radar images), for example, aninspection is performed to determine whether the object 800 has asuspicious object.

Note that, non-patent literature 2 describes a method for measuring thevelocity of an object in an image by estimating the optical flow betweenimage frames.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laid-Open No. H11-94931

Non-Patent Literature

NPL 1: D. M. Sheen, et al., “Three-Dimensional Millimeter-Wave Imagingfor Concealed Weapon Detection,” IEEE Transactions on Microwave Theoryand Techniques, vol. 49, No. 9, September 2001

NPL 2: B. D. Lucas, T. Kanade, “An iterative image registrationtechnique with an application to stereo vision,” Proc. 7th InternationalJoint Conference on Artificial Intelligence, pp. 674-679, 1981

SUMMARY OF INVENTION Technical Problem

FIG. 19 is a block diagram showing an example configuration of a generalradar device. The radar device 901 shown in FIG. 19 includes atransmission antenna (Tx) 102 that emits electromagnetic waves, areceiving antenna (Rx) 103 that receives reflected electromagneticwaves, a radar signal transmission and receiving unit 904, and animaging processing unit 905. The transmission antenna 102 and thereceiving antenna 103 correspond to the radar 804 in FIG. 18. Althoughone transmission antenna 102 and one receiving antenna 103 areillustrated in FIG. 19, practically, a large number of transmissionantennas 102 and a large number of receiving antennas 103 are installed.Hereinafter, the system including the transmission antenna, thereceiving antenna, and the radar device is referred to as a radarsystem.

The radar signal transmission and receiving unit 904 makes thetransmission antenna 102 emit electromagnetic waves. The radar signaltransmission and receiving unit 904 inputs a radar signal from thereceiving antenna 103. The imaging processing unit 905 generates a radarimage based on the radar signal.

FIG. 20 is a schematic diagram showing an example of an antennaarrangement in an electronically scanned array including a plurality oftransmission antennas 102 and a plurality of receiving antennas 103. Athree-dimensional coordinate system is also shown in FIG. 20. Theelectronically scanned array comprises, for example, Multiple-Input andMultiple-Output (MIMO) in which a plurality of transmission antennas 102transmit signals of the same frequency. The electronically scanned arraymay also comprise a monostatic transmission and receiving antennaelement in which the transmission antenna 102 and the receiving antenna103 are common. The array may be comprised so that radar signals arecaptured through the receiving antenna 103 while the transmissionantenna 102 that irradiates electromagnetic waves from the plurality oftransmission antennas 102 is switched.

An imaging device that applies electromagnetic waves, such as a generalbody scanner, is intended to image a stationary object 800. That is, theradar device 901 generates a radar image based on the assumption thatthe object is stationary when it is irradiated with electromagneticwaves. FIG. 21 is an explanatory diagram showing an example of a radarimage of a stationary object 800.

When the object 800 moves, such as when the object 800 walks through thepassage 801 without constraint in its movement, a blur (image blur) mayoccur in the radar image, as illustrated in FIG. 22. When the bluroccurs, a detection object (for example, a suspicious object)accompanying the object 800 may be buried in the radar image. Therefore,when the radar image is used for various purposes, it is desirable togenerate a radar image in which the blur is suppressed.

In addition, in the case where the object 800 moves without constraint,it is difficult to predict the movement of the object 800, and it isdifficult to suppress the blur by taking the movement of the object 800into account.

Patent literature 1 describes a radar device that generates an image bycorrelation processing on two video signals based on received signals ofa receiving radar having different obtainment times. The radar devicedescribed in patent literature 1 predicts the position of an object inone video signal in the other video signal, and corrects the position ofthe object in the other video signal to the predicted position. However,there is no disclosure of blur suppression in patent literature 1.

It is an object of the present invention to provide a radar system, animaging method and an imaging program capable of generating a radarimage with suppressed blur even when an object is moving.

Solution to Problem

A radar system according to the present invention includes a pluralityof transmission antennas which irradiate electromagnetic waves, aplurality of receiving antennas which receive the irradiatedelectromagnetic waves that have been reflected and generatingmeasurement signals, radar signal transmission and receiving means forobtaining the measurement signals, movement estimation means forestimating a movement of an object, and motion-compensated imagegeneration means for generating a radar image, based on the measurementsignals and the estimated object movement.

An imaging method according to the present invention includes obtainingthe measurement signals based on reflected waves of electromagneticwaves irradiated from a plurality of transmission antennas, estimating amovement of an object, and generating a radar image, based on themeasurement signals and the estimated object movement.

An imaging program according to the present invention causes a computerto execute a process of obtaining the measurement signals based onreflected waves of electromagnetic waves irradiated from a plurality oftransmission antennas, a process of estimating a movement of an object,and a process of generating a radar image based on the measurementsignals and the estimated object movement.

Advantageous Effects of Invention

According to the present invention, it is possible to obtain a radarimage with suppressed blur even when an object is moving.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] It depicts a block diagram showing a configuration example ofthe radar system of the first example embodiment.

[FIG. 2] It depicts an explanatory diagram showing a position of anobject at the irradiation time.

[FIG. 3] It depicts an explanatory diagram showing a position of anobject at each time.

[FIG. 4] It depicts an explanatory diagram showing imaging time of aradar image and movement amount of an object.

[FIG. 5] It depicts an explanatory diagram showing estimated movementamount and its correlation value.

[FIG. 6A] It depicts a flowchart showing the operation of the radarsystem of the first example embodiment.

[FIG. 6B] It depicts a flowchart showing the operation of the radarsystem of the first example embodiment.

[FIG. 6C] It depicts a flowchart showing the operation of the radarsystem of the first example embodiment.

[FIG. 7] It depicts a block diagram showing a configuration example ofthe radar system of the second example embodiment.

[FIG. 8] It depicts an explanatory diagram showing an example of aninterest point extracted by corner detection.

[FIG. 9A] It depicts a flowchart showing the operation of the radarsystem in the second example embodiment.

[FIG. 9B] It depicts a flowchart showing the operation of the radarsystem in the second example embodiment.

[FIG. 9C] It depicts a flowchart showing the operation of the radarsystem in the second example embodiment.

[FIG. 10] It depicts a block diagram showing a configuration example ofthe radar system of the third example embodiment.

[FIG. 11] It depicts an explanatory diagram showing an example of anarea divided image based on an interest point.

[FIG. 12] It depicts an explanatory diagram showing the movement amountcorresponding to the area obtained by division.

[FIG. 13A] It depicts a flowchart showing the operation of the radarsystem of the third example embodiment.

[FIG. 13B] It depicts a flowchart showing the operation of the radarsystem of the third example embodiment.

[FIG. 13C] It depicts a flowchart showing the operation of the radarsystem of the third example embodiment.

[FIG. 14] It depicts a block diagram showing a configuration example ofthe radar system of the fourth example embodiment.

[FIG. 15] It depicts a flowchart showing the operation of the radarsystem of the fourth example embodiment.

[FIG. 16] It depicts a block diagram showing an example of a computerwith a CPU.

[FIG. 17] It depicts a block diagram showing the main part of the radarsystem.

[FIG. 18] It depicts an explanatory diagram showing a body scannersystem.

[FIG. 19] It depicts a block diagram showing a configuration example ofa general radar system.

[FIG. 20] It depicts a schematic diagram showing an example of anantenna arrangement in an electronically scanned array including aplurality of transmission antennas and a plurality of receivingantennas.

[FIG. 21] It depicts an explanatory diagram showing an example of aradar image of a stationary object.

[FIG. 22] It depicts an explanatory diagram for explaining a blur causedby the movement of an object.

DESCRIPTION OF EMBODIMENTS

Hereinafter, example embodiments of the present invention are describedwith reference to the drawings.

Example Embodiment 1

FIG. 1 is a block diagram showing a configuration example of the radarsystem of the first example embodiment. The radar system of the firstexample embodiment includes a radar device 101, a transmission antenna102, a receiving antenna 103, an external sensor (hereinafter, referredto as a sensor) 105. Although FIG. 1 illustrates one transmissionantenna 102 and one receiving antenna 103, practically, a large numberof transmission antennas 102 and a large number of receiving antennas103 are installed.

The radar device 101 includes a radar signal transmission and receivingunit 104 that instructs the transmission antenna 102 and the receivingantenna 103 to transmission and receiving electromagnetic waves, amovement estimation unit 106 that has a function of estimating amovement of an object 800 (refer to FIG. 18) that may appear in theradar image, and a motion-compensated image generating unit 112 thatgenerates a radar image using the radar signals and the estimated objectmovement.

When the transmission antenna 102 receives an irradiation instructionfrom the radar signal transmission and receiving unit 104, thetransmission antenna 102 starts irradiating electromagnetic waves. Forexample, a continuous wave (CW), a frequency modulated continuous wave(FMCW), and a stepped FMCW can be used as the electromagnetic wave to beirradiated from the transmission antenna 102. Hereinafter, it is assumedthat Stepped FMCW, whose frequency changes according to time, is used,but the use of Stepped FMCW is an example. The frequency of anelectromagnetic wave is expressed as f(t).

The receiving antenna 103 receives a reflected wave of theelectromagnetic wave irradiated by the transmission antenna 102, andoutputs a measurement signal (radar signal) based on the reflected waveto the radar signal transmission and receiving unit 104. Hereafter, theradar signal based on the reflected wave received at time t by thereceiving antenna j from the electromagnetic wave irradiated by thetransmission antenna i is expressed as s_(i,j)(t).

The radar signal transmission and receiving unit 104 instructs thetransmission antenna 102 to irradiate electromagnetic waves according toa predetermined irradiation order and irradiation time. The radar signaltransmission and receiving unit 104 inputs a radar signal from thereceiving antenna 103. The radar signal transmission and receiving unit104 outputs the radar signal and the irradiation time (irradiation starttime) of the electromagnetic wave of the transmission antenna 102 to themotion-compensated image generating unit 112. The radar signaltransmission and receiving unit 104 also outputs the radar signal andthe irradiation time of the electromagnetic wave of the transmissionantenna 102 to the movement estimation unit 106, if necessary.

The sensor 105 outputs the position or velocity (specifically, dataindicating the position or velocity) or image of the object 800 to themovement estimation unit 106. However, if the movement of the object isestimated based on the radar image in the movement estimation unit 106,the sensor 105 is not necessary.

The following description illustrates a case in which the exampleembodiment is applied to the body scanner system illustrated in FIG. 18.However, the application of this and other example embodiments is notlimited to body scanner systems. As illustrated in FIG. 18, an object800 walks in the x direction. The radar 804 used to generate the radarimage is installed on a side panel 803. It is assumed that a MIMOantenna (refer to FIG. 20) comprising a plurality of transmissionantennas 102 and receiving antennas 103 is used as the radar 804.

Note that this example embodiment and other example embodiments areeffective for the movement of any object 800. This example embodimentand other example embodiments are also effective for a radar installedat arbitrary position. In other words, the installation position of theradar 804 illustrated in FIG. 18 is an example. In addition, in this andother example embodiments, in order to suppress blur caused by movementof the object 800 during irradiation of electromagnetic waves from thetransmission antenna 102, a radar imaging system using a plurality oftransmission antennas 102, or a radar imaging system that uses aplurality of frequencies radar imaging system and a plurality oftransmission antennas 102 and a plurality of frequencies.

Hereinafter, the number of transmission antennas is N_(tx), the numberof receiving antennas is N_(rx), the speed of light is c, and theirradiation time of each transmission antenna 102 (respectiveirradiation start time) is t_(i) (i=1, 2, 3, . . . , N_(tx)). Inaddition, the case where a radar image is generated from radar signalsby all transmission antennas 102 and all receiving antennas 103 is usedas an example. Note that, for simplicity of explanation, the case whereeach of the transmission antennas 102 irradiates electromagnetic wavesonly once is used as an example. However, practically, the irradiationof electromagnetic waves from each of the transmission antennas 102 isrepeated. The irradiation times of each transmission antenna are assumedto be equally spaced.

The case is assumed as an example where the radar device 101 performsimaging with motion compensation using the object position at theirradiation time (irradiation start time in the whole) ti as thecompensation reference position. That is, in FIG. 2, when the positionof the object 800 at the irradiation time ti is position #1 and theposition of the object 800 at the irradiation time t_(Ntx) is position#2, the radar device 101 performs imaging (in this example embodiment,motion-compensated imaging) with position #1 as the reference. Note thatthose conditions are examples for simplicity of explanation, and thisexample embodiment and other example embodiments are not limited bythose conditions.

The movement estimation unit 106 includes an image database (image DB)107 that stores images and imaging times, an image generating unit 108that generates a radar image using radar signals from the radar signaltransmission and receiving unit 104 as an input and stores the radarimage and the imaging time in the image DB 107, and a movement amountestimation unit 110 that estimates the movement of the object based onthe images with different imaging times.

The movement estimation unit 106 inputs a signal from the sensor 105 orthe radar signal and outputs the estimated movement amount of the object800 at the irradiation time of each transmission antenna 102 to themotion-compensated image generating unit 112. There are several possibleestimation methods for the movement estimation unit 106. Example are thefollowing methods.

Method A:

The movement estimation unit 106 estimates the movement of the object800 based on the signals from the sensor 105. The movement estimationunit 106 obtains, for example, a position or a velocity of the object800 from the sensor 105, and estimates the movement amount from them. Asthe sensor 105, for example, an ultrasonic sensor, VICON (a motioncapture system by Vicon Motion Systems), a radar that measures distanceand velocity, and the like can be used. The sensor 105 is installed at apoint on the object 800 where its velocity is easily obtained relativeto its movement. For example, the sensor 105 is installed in front ofthe direction of movement of the object 800.

When the information obtained from the sensor 105 is information of theposition of the object 800, the result is as shown in FIG. 3. FIG. 3 isan explanatory diagram showing a position of an object at each time.Specifically, FIG. 3 shows a graph in which the estimated position P′(t)of the object 800 at time t and the actual position P(t) of the object800 are plotted. The movement estimation unit 106 can calculate themovement amounts Δ(t_(i)) of the object at the irradiation time of theelectromagnetic wave of each transmission antenna 102 from the estimatedposition P′(t) using the following equation (1). Note that if a sensor105 outputting a signal indicating position or velocity information isused, the signal may be temporarily stored in a DB.

[Math. 1]

{right arrow over (Δ(t _(l)))}=P′(t _(i))−P′(t ₁)   (1)

Suppose that the estimated position P′(t) is expressed bythree-dimensional data of x, y, and z. When a sensor 105 that outputsone-dimensional or two-dimensional data is used, the movement estimationunit 106 estimates only the movement amount of the obtainedone-dimensional or two-dimensional data. When the information obtainedfrom the sensor 105 is the velocity of the object at the irradiationtime, v_(xyz)(t)={vx, vy, vz}, the movement amount of the object 800,Δ(ti) can be calculated using the following equation (2), assuming thatthe velocity of the object 800 in the irradiation period is constant.

[Math. 2]

{right arrow over (Δ(t _(l)))}=(vx·(t _(i) −t ₁), vy·(t _(i) −t ₁),vz·(t _(i) −t ₁))   (2)

Method B:

The movement estimation unit 106 estimates the movement of the object800 based on an image from the sensor 105. When Method B is adopted, inthe movement estimation unit 106, the image DB 107 stores images andimaging times. The movement amount estimation unit 110 estimates themovement of the object based on the images with different imaging times.As the sensor 105, for example, a two-dimensional camera, a depthcamera, or the like can be used. Note that it is assumed that the sensor105 is installed at the same position as the radar 804 (i.e., on theside panel 803 in FIG. 18).

Method C:

The movement estimation unit 106 estimates the movement of the objectusing a radar image based on the radar signals obtained from thereceiving antenna 103. When Method C is adopted, the image generatingunit 108 that generates a radar image based on the radar signals isutilized in the movement estimation unit 106. The image DB 107 storesthe radar images and the imaging times. The movement amount estimationunit 110 estimates the movement of the object based on the radar imageswith different imaging times.

Note that, in the case where Method A or Method B is adopted, the imagegenerating unit 108 may not be comprised in the movement estimation unit106.

When Method C is used, the image generating unit 108 inputs radarsignals from the radar signal transmission and receiving unit 104,generates radar images, and stores the radar images and the imagingtimes in the image DB 107. The image generating unit 108 calculates theimaging time based on each irradiation time of the transmission antenna102 received from the radar signal transmission and receiving unit 104.The image generating unit 108, for example, assumes that the imagingtime of the radar image is (t_(Ntx)+t₁)/2, which is an average value ofthe irradiation times, when all the transmission antennas 102 are used.The image generating unit 108 generates the radar image by beamforming,for example. That is, the image generating unit 108 generates the radarimage using the following equations (3) and (4). Note that the method ofgenerating the radar image is not limited to beamforming. The imagegenerating unit 108 can generate the radar image using any imagingmethod.

$\begin{matrix}\left\lbrack {{Math}.3} \right\rbrack &  \\{{{vim}{g_{i,j}\left( \overset{\rightarrow}{v} \right)}} = {\sum_{i}^{Ntx}{\sum_{j}^{Nrx}{{s_{i,j}(t)}*e^{\frac{2\pi{j \cdot {f(t)}}}{c}{\{{{❘{\overset{\rightarrow}{R_{\iota}} - \overset{\rightarrow}{v}}❘} + {❘{\overset{\rightarrow}{R_{J}} - \overset{\rightarrow}{v}}❘}}\}}}}}}} & (3) \\\left\lbrack {{Math}.4} \right\rbrack & \\{{{vimg}\left( \overset{\rightarrow}{v} \right)} = {\sum_{i}^{Ntx}{\sum_{j}^{Nrx}{vimg_{i,j}\left( \overset{\rightarrow}{v} \right)}}}} & (4)\end{matrix}$

Take v(v ∈ V) for an imaging position when the whole area of the radarimage is V. vimg_(i,j)(v) is an radar image of the imaging position vgenerated from the radar signals by the transmission antenna i and thereceiving antenna j, respectively. |R_(i)−v| and |R_(j)−v| denotedistances from the imaging position v to the transmission antenna i andthe receiving antenna j, respectively. vimg(v) is the final radar imageat the imaging position v. s_(i,j)(t) is the radar signal.

The plurality of radar images with different imaging times may notnecessarily be generated based on the same combination of transmissionantenna and receiving antenna. However, if the radar images are notgenerated based on the same combination of transmission antenna andreceiving antenna, transmission and receiving antenna pairs each ofwhich is combination of the transmission antenna 102 and the receivingantenna 103, that center positions of antenna apertures formed by thepairs are the same or close (for example, adjacent), are used.Alternatively, a plurality of radar images with different imaging timesare generated under the conditions that the number of transmissionantennas is the same, the irradiation time of electromagnetic waves ofthe transmission antennas is the same, and the aperture lengths by thetransmission antenna and the receiving antenna are the same. Forexample, in a MIMO configuration consisting of four radar modules witheight transmission antennas and eight receiving antennas as illustratedin FIG. 20, the movement amount of the object 800 may be estimated bycomparing a radar image generated by half of the transmission antennasirradiating electromagnetic waves in the first half of the period with aradar image generated by the remaining transmission antennas irradiatingelectromagnetic waves in the second half of the period that were notused in the first half of the period.

When Method B or Method C is used, the movement amount estimation unit110 estimates the movement amount of the object 800 by image processingbased on images (radar images or images from the sensor 105) withdifferent imaging times. However, the difference time of the imagingtimes of the images used is substantially short for the movement of theobject 800. For example, the difference time is less than or equal to atime interval that can be approximated by first order approximation(Taylor expansion in one dimension) when the position of the object 800is expressed as a function of time. As with the case where Method A isused, there are primarily two methods of estimating the movement amountof the object 800.

In the first method, the movement amount estimation 110 first uses asingle image. The movement amount estimation unit 110 estimates aposition of the object from the single image. Next, the movement amountestimation unit 110 derives the estimated position P′(t), for example,by linear regression from the estimated positions of the object in aplurality of images with different imaging times. Then, the movementamount estimation unit 110 calculates the movement amount Δ(t_(i)) ofthe object using the equation (1). When the area or volume of the object800 is large, the movement amount estimation unit 110 can use, forexample, the centroid of the object 800 as the position of the object800.

In the second method, the movement amount estimation unit 110 usesimages with different imaging times and estimates the movement amount bycomparing the plurality of images. The movement amount estimation unit110 can, for example, use a point where the correlation value is high(shift value) among the images as the movement amount. The movementamount estimation unit 110 may also utilize phase only correlation or anoptical flow-based method as described in non-patent literature 2. Whenthe difference time of the imaging times is greater than the sum of theirradiation times of all the transmission antennas 102, the movementamount estimation unit 110 may calculate the movement velocity of theobject 800 by dividing the calculated movement amount by the differencetime of the imaging times, and estimate the movement amount using, forexample, equation (2). In this case, it is assumed that the movementvelocity of the object 800 is constant between different imaging times.

When Method C is used, for example, when the movement amount of theobject 800 estimated from the images at the imaging times T₁, T₂ is d,the movement velocity of the object 800 is v_(xyz)(t)=d/(T₁−T₂). Thismovement velocity corresponds to the slope of the estimated positionP′(t) in FIG. 4. The movement amount estimation unit 110 can estimatethe movement amount of the object 800 at each irradiation time using themovement velocity of the object 800 and the equation (2).

When the shift value (movement amount) is estimated based on thecorrelation between radar images, the result is obtained as shown inFIG. 5. FIG. 5 shows an example of the estimated movement amount and itscorrelation value. The movement amount estimation unit 110 may use onlyd₁ which has the highest correlation value, as the movement amount. Ifthere are a plurality of peaks, the movement amount estimation unit 110may select a plurality of movement amounts such as d₁ and d₂. Themovement amount estimation unit 110 may also use an average value of d₁and d₂ as the movement amount.

Note that FIG. 5 shows only the movement amount in one dimension (x, y,or z) as an example, and the movement amount estimation unit 110 canalso estimate the movement amount in three dimension by takingcorrelation for three-dimensional images. In the case where the opticalflow-based method is used, when a plurality of values are estimated asthe movement amount of the object 800, the movement amount estimationunit 110 may select the maximum value or the average value, or aplurality thereof.

The motion-compensated image generating unit 112 generates a radar imagebased on the radar signals input from the radar signal transmission andreceiving unit 104 and the movement amounts of the object at theirradiation times of the respective transmission antennas 102 input fromthe movement estimation unit 106. The motion-compensated imagegenerating unit 112 outputs the generated radar image. Themotion-compensated image generating unit 112 performs, for example,motion-compensated imaging based on beamforming. That is, themotion-compensated image generating unit 112 obtains themotion-compensated final radar image by using the following equation(5), using the movement amounts Δ(t_(i)) of the object at theirradiation times of the electromagnetic waves of the respectivetransmission antennas 102.

[Math. 5]

vimg({right arrow over (v)})=Σ_(i) ^(Ntx)Σ_(j) ^(Nrx) vimg_(i,j)({rightarrow over (v)}+{right arrow over (Δ(t _(l)))})   (5)

When generating the final radar image, the motion-compensated imagegenerating unit 112 shifts the imaging position for each transmissionantenna 102 by the movement amount and adds the plurality of radarimages together. In equation (5), it is assumed that there is nomovement of the object 800 during the irradiation period of theelectromagnetic wave by one transmission antenna 102. However, if themovement amount of the object 800 during irradiation with onetransmission antenna 102 (while changing the frequency) is large, themotion-compensated image generating unit 112 should shift the imagingposition by the movement amount in units of frequency. If there aremultiple movement amounts of the object 800 received from the movementestimation unit 106, the motion-compensated image generating unit 112can perform motion-compensated imaging using the equation (5) for eachmovement amount.

Next, the operation of the radar system in the first example embodimentwill be described with reference to the flowcharts of FIGS. 6A-6C. FIG.6A shows the entire processing of the radar system. FIG. 6B and FIG. 6Cshow processes executed by the movement estimation unit 106.

The radar signal transmission and receiving unit 101 makes the pluralityof transmission antennas 102 emit electromagnetic waves sequentiallyaccording to a predetermined irradiation order, and obtains radarsignals based on the reflected waves received by the receiving antennas103 (step S101). The radar signal transmission and receiving unit 104outputs the radar signal and the irradiation time of each transmissionantenna to the motion-compensated image generating unit 112.

Note that the movement amount estimation of the object 800 based on thesignal (signal that can identify the position or velocity or image ofthe object 800) from the sensor 105 and the movement amount estimationbased on the radar image are executed alternatively. When the radardevice 101 is configured to perform the movement amount estimation basedon the radar image, the radar signal transmission and receiving unit 104also outputs the radar signal and the irradiation time of eachtransmission antenna to the movement estimation unit 106.

In step S102, the movement estimation unit 106 inputs signals related tothe position, velocity, or image of the object 800 from the sensor 105.When the sensor 105 capable of outputting an image is used, the imagefrom the sensor 105 is stored in the image DB 107. Note that in the casewhere the radar device 101 is configured to perform movement amountestimation based on the radar image, the movement estimation unit 106does not execute the processing of step S102. In addition, when theradar device 101 is so configured, the sensor 105 need not be installedas described above.

In the movement estimation unit 106, the movement amount estimation unit110 estimates the movement amount of the object 800 at the irradiationtime of each transmission antenna 102 (step S103). The movement amountestimation unit 110 outputs the estimated movement amount of the object800 to the motion-compensated image generating unit 112.

When the above described Method B is used, the processing of step S103Bshown in FIG. 6B is executed as the processing of step S103. That is,the images from the sensor 105 are stored in the image DB 107 (stepS131), and the movement amount estimation unit 110 estimates themovement amount of the object 800 at the irradiation time of eachtransmission antenna 102 based on the images of different imaging timesstored in the image DB 107 (step S132).

When the above described Method C is used, the processing of step S103Cshown in FIG. 6C is executed as the processing of step S103. That is,first, in the movement estimation unit 106, the image generating unit108 inputs the radar signal from transmission and receiving unit 104,and generates a radar image (step S134). The image generating unit 108stores the generated radar image and the imaging time in the image DB107 (step S135). The movement amount estimation unit 110 estimates themovement amount of the object 800 at the irradiation time of eachtransmission antenna 102 based on the radar images of different imagingtimes stored in the image DB 107 (step S136).

Note that when the above described Method A is used, the movement amountestimation unit 110 can estimate the movement amount of the object 800directly from the signal from the sensor 105.

The motion-compensated image generating unit 112 generates a radar imagefrom the radar signals input from the radar signal transmission andreceiving unit 104 based on the estimated movement amount input from themovement estimation unit 106, for example, using the equation (5) (stepS104).

In this example embodiment, the radar device 101 estimates the movementof the object 800 using the information (information of position orvelocity) or the image obtained from the sensor 105, or the radar image.Then, the radar device 101 generates a radar image by compensating forthe estimated movement of the object 800. As a result, a radar imagewith blur suppressed is obtained.

Example Embodiment 2

FIG. 7 is a block diagram showing a configuration example of the radarsystem of the second example embodiment. The radar system of the secondexample embodiment includes a radar device 201, a transmission antenna102, a receiving antenna 103, and a sensor 105. Although onetransmission antenna 102 and one receiving antenna 103 are illustratedin FIG. 7, practically, a large number of transmission antennas 102 anda large number of receiving antennas 103 are installed.

The radar device 201 includes a radar signal transmission and receivingunit 104, a movement estimation unit 206 that estimates a movement of anobject, and a motion-compensated image generating unit 212 thatgenerates a radar image using radar signals and the estimated movementof the object.

The movement estimation unit 206 includes an image DB 107, an imagegenerating unit 108, an interest point extraction unit 209 that extractsone or more interest points in the object 800, and a movement amountestimation unit 210 that estimates the movement of the object based onimages with different imaging times. The movement amount estimation unit210 in the movement estimation unit 206 estimates the movement of theinterest points. In this example embodiment, in the movement estimationunit 206, the movement amount estimation unit 210 estimates the movementamount for each interest point extracted by the interest pointextraction unit 209.

The transmission antenna 102, the receiving antenna 103, the radarsignal transmission and receiving unit 104, the sensor 105, the image DB107, and the image generating unit 108 have the same functions as thoseof the first example embodiment.

Similar to the movement estimation unit 106 in the first exampleembodiment, the movement estimation unit 206 can input the signal fromthe sensor 105 or the radar signal and use three methods (Method A,Method B, and Method C). In this example embodiment, the movementestimation unit 206 outputs the movement amount for each interest pointat the irradiation time of each transmission antenna 102 to themotion-compensated image generating unit 212.

When Method A is used, the movement estimation unit 206 estimates themovement amount for each interest point in a process similar to theprocess by the movement estimation unit 106 in the first exampleembodiment. For example, when the object 800 is a pedestrian, themovement estimation unit 206 estimates the movement amount for each partsuch as a hand, a foot, and a torso.

When Method B or Method C is used, the interest point extraction unit209 extracts one or more interest points from the images (radar imagesor images from the sensor 105) stored in the image DB 107. The interestpoint extraction unit 209 outputs the positions of the extractedinterest points and the images with different imaging times to themovement amount estimation unit 210. For example, the interest pointextraction unit 209 automatically extracts the interest point from theimage of the imaging time close to the irradiation time that becomes thereference position by corner detection or the like. The interest pointextraction unit 209 may extract a predetermined point. The predeterminedpoint is, for example, a point on a grid that divides the image intoequal intervals.

FIG. 8 is an explanatory diagram showing an example of an interest pointextracted by corner detection. Image #1 is an image at an imaging timeclose to the irradiation time that becomes a reference position. Image#2 is an image at an imaging time different therefrom. In the exampleshown in FIG. 8, interest points #1, #2, #3, and #4 are extracted fromimage #1. The extracted interest points are denoted as pk (1≤k≤Np).

When an interest point is extracted based on the image obtained from thesensor 105, the coordinates of the interest point are transformed intothe coordinates of the image obtained by the radar device 201. Existingalignment (registration) techniques and the like can be used for thecoordinate transformation.

The movement amount estimation unit 210 estimates the movement amount ofeach interest point at the irradiation time of each transmission antenna102 using images with different imaging times. The movement amountestimation unit 210 outputs the estimated movement amount to themotion-compensated image generating unit 212. In the example shown inFIG. 8, an arrow extending from each interest point represents themovement amount of each interest point. The movement amount estimationunit 210 can use an existing correlation method, optical flow, or thelike, when estimating the movement amount of each interest point.Assuming that the movement amount of each interest point at theirradiation time of each transmission antenna 102 is Δ_(p)(t_(i)), themovement amount of each interest point can be expressed by the followingequation (6). In equation (6), P′p(t_(i)) indicates the estimatedposition of the interest point pk at time t_(i).

[Math. 6]

{right arrow over (Δ_(p)(t _(l)))}=P′ _(p)(t _(i))−P′ _(p)(t ₁)   (6)

When v_(p,xyz)(t)={vx_(p), vy_(p), vz_(p)} is assumed as the velocity ofeach interest point calculated from the movement amount of the interestpoint estimated between images with different imaging times and thedifference time of the imaging times, the movement amount estimationunit 210 can calculate the movement amount of each interest point by thefollowing equation (7) as well as equation (2).

[Math. 7]

{right arrow over (Δ_(p)(t _(l)))}=(vx _(p)·(t _(i) −t ₁), vy _(p)·(t_(i) −t ₁), vz _(p)·(t _(i) −t ₁))   (7)

The motion-compensated image generating unit 212 generates a radar imagebased on the radar signal input from the radar signal transmission andreceiving unit 104 and the movement of each interest point at anirradiation time of each transmission antenna 102 input from themovement estimation unit 206. The motion-compensated image generatingunit 212 outputs the generated radar image. The motion-compensated imagegenerating unit 212 performs, for example, motion-compensated imagingbased on beamforming. That is, the motion-compensated image generatingunit 212 obtains a motion-compensated radar image using the followingequation (8) by using the movement amount Δ_(p)(t_(i)) of each interestpoint of the object at the irradiation time of the electromagnetic waveof each transmission antennas 102.

[Math. 8]

vimg_(p)({right arrow over (v)})=Σ_(i) ^(Ntx)Σ_(j) ^(Nrx)vimg_(i,j)({right arrow over (v)}+{right arrow over (Δ_(p)(t _(l)))})  (8)

N_(p), which is the number of interest points, radar images aregenerated based on the equation (8). Similar to the equation (5), it isassumed that there is no movement of the object 800 during theirradiation period of the electromagnetic wave at one transmissionantenna 102 in the equation (8). However, if the movement amount of theobject 800 during irradiation with one transmission antenna 102 (whilechanging the frequency) is large, the motion-compensated imagegenerating unit 212 should shift the imaging position by the movementamount in units of frequency.

Next, the operation of the radar system of the second example embodimentwill be described with reference to the flowcharts of FIGS. 9A-9C. FIG.9A shows the entire processing of the radar system. FIG. 9B and FIG. 9Cshow processes executed by the movement estimation unit 206.

The processing of steps S101 and S102 is the same as the processing inthe first example embodiment.

In this example embodiment, the movement amount estimation of the object800 based on the signal (signal that can identify the position orvelocity or image of the object 800) from the sensor 105 and themovement amount estimation based on the radar image are also executedalternatively. When the radar device 201 is configured to perform themovement amount estimation based on the radar image, the radar signaltransmission and receiving unit 104 also outputs the radar signal andthe irradiation time of each transmission antenna to the movementestimation unit 206.

In the case where the radar device 201 is configured to perform themovement amount estimation based on the radar image, the movementestimation unit 206 does not execute the processing of step S102. In thecase where the radar device 201 is so configured, the sensor 105 neednot be installed as described above.

In the movement estimation unit 206, the movement amount estimation unit210 estimates the movement amount of the object 800 (step S203). Themovement amount estimation unit 210 outputs the estimated movementamount of the object 800 to the motion-compensated image generating unit212.

When Method B described above is used, the processing of step S203Bshown in FIG. 9B is executed as the processing of step S203. That is,the image from the sensor 105 is stored in the image DB 107 (step S231),and the interest point extraction unit 209 extracts one or more interestpoints pk from the image from the sensor 105 stored in the image DB 107(step S232). Note that the processing of step S231 is the same as theprocessing of step S131 in the first example embodiment. The interestpoint extraction unit 209 outputs the extracted positions of theinterest points and the images with different imaging times to themovement amount estimation unit 210. The movement amount estimation unit210 estimates the movement amount Δ_(p)(t_(i)) for each interest point(step S233). The movement amount estimation unit 210 outputs theestimated movement amounts of the interest points to themotion-compensated image generating unit 212.

When the above described Method C is used, the processing of step 5203Cshown in FIG. 9C is executed as the processing of step S203. That is, inthe movement estimation unit 206, the image generating unit 108 inputsradar signals from the radar signal transmission and receiving unit 104,and generates a radar image (step S234). The image generating unit 108stores the generated radar image and the imaging time in the image DB107 (step S235). Note that the processing of steps S234 and S235 is thesame as the processing of steps S134 and S135 in the first exampleembodiment. The interest point extraction unit 209 extracts one or moreinterest points pk from the radar images of different imaging timesstored in the image DB 107 (step S236). The interest point extractionunit 209 outputs the extracted positions of the interest points and theradar images with different imaging times to the movement amountestimation unit 210. The movement amount estimation unit 210 estimatesthe movement amount for each interest point. The movement amountestimation unit 210 outputs the estimated movement amounts of theinterest points to the motion-compensated image generating unit 212.

The motion-compensated image generating unit 212 generates a radar imagefrom the radar signals input from the radar signal transmission andreceiving unit 104, based on the estimated movement amount from themovement estimation unit 206, using equation (8), for example (stepS104).

In this example embodiment, the radar device 201 estimates the movementof each interest point in the object 800 using information (position orvelocity information) or images obtained from the sensor 105, or radarimages. Then, the radar device 201 generates a radar image bycompensating for the movements of the estimated interest points. As aresult, a radar image is obtained in which blurring caused by differentmovements at multiple positions in the object 800 is suppressed.

Example Embodiment 3

FIG. 10 is a block diagram showing a configuration example of the radarsystem of the third example embodiment. The radar system of the thirdexample embodiment includes a radar device 301, a transmission antenna102, a receiving antenna 103, and a sensor 105. Although onetransmission antenna 102 and one receiving antenna 103 are illustratedin FIG. 10, practically, a large number of transmission antennas 102 anda large number of receiving antennas 103 are installed.

The radar device 301 includes a radar signal transmission and receivingunit 104, a movement estimation unit 206 that estimates a movement of anobject, an image area divider 311 that divides a radar image into areas,and a motion-compensated image generating unit 312 that generates aradar image using the radar signals and the estimated movement of theobject.

The transmission antenna 102, the receiving antenna 103, the radarsignal transmission and receiving unit 104, the sensor 105, and themovement estimation unit 206 have the same functions as those of thesecond example embodiment shown in FIG. 7. Accordingly, the image DB107, the image generating unit 108, the interest point extraction unit209, and the movement amount estimation unit 210 have the same functionsas those of the second example embodiment.

In this example embodiment, the movement estimation unit 206 inputs thesignal from the sensor or the radar signal, and outputs the movementamount for each interest point and the position of the interest point atthe irradiation time of each transmission antenna 102 to the image areadivider 311.

The image area divider 311 divides the image (radar image or image fromthe sensor 105) into areas based on the positions of the interestpoints. The image area divider 311 outputs the area obtained by thedivision and the movement amount of the corresponding interest point tothe motion-compensated image generating unit 312. The image area divider311 can, for example, divide an image by clustering with an interestpoint as a mother point. As a division method, for example, division bya Voronoi diagram can be used. That is, the image area divider 311 candivide an image into areas (area division) by mapping a pixel (in thiscase, an imaging position) in the image to the nearest interest pointamong a plurality of interest points (kernel points), and defining anarea in which the pixel corresponding to the interest point is anelement.

FIG. 11 is an explanatory diagram showing an example of an area dividedimage based on an interest point. FIG. 11 shows an example of an areadivided based on the position of an interest point in image #1illustrated in FIG. 8.

The areas corresponding to the interest points #1, #2, #3, and #4 denotethe areas #1, #2, #3, and #4. The whole area of the image denotes v ∈ V,and the divided areas denote v_(p) ∈ V_(p)(p=1, 2, . . . , N_(p)), whichcan be expressed in general as {V₁ ∪ V₂ ∪ . . . V_(Np)}=V.

The motion-compensated image generating unit 312 generates a radar imagefor each area based on the radar signals input from the radar signaltransmission and receiving unit 104 and the movement of an interestpoint corresponding to the area obtained by the division. Themotion-compensated image generating unit 312 outputs the generated radarimage. That is, the motion-compensated image generating unit 312 obtainsa motion-compensated radar image using the following equation (9) foreach area v_(p) ∈ V_(p) in the image, using the movement amountΔ_(p)(t_(i)) for each interest point of the object at the irradiationtime of the electromagnetic waves of the respective transmissionantennas 102.

[Math. 9]

vimg({right arrow over (v _(p))})=Σ_(i) ^(Ntx)Σ_(j) ^(Nrx) vimg({rightarrow over (v _(p))}+{right arrow over (Δ_(p)(t _(l)))})   (9)

FIG. 12 is an explanatory diagram showing the movement amountcorresponding to the area obtained by division. Imaging is performed forthe area #1 and the area #3 shown in FIG. 11 based on different movementamounts Δ₁(t_(i)) and Δ₃(t_(i)). In FIG. 12, the thin dotted lineindicates the area #1. The solid thin line indicates the area #3. Thebold dotted line indicates the area #1 shifted by the movement amount ofthe interest point corresponding to the area #1. The bold solid lineindicates the area #3 shifted by the movement amount of the interestpoint corresponding to the area #3. Since the same calculation isperformed for an overlapped part by the areas that are shifted by themovement amount, the motion-compensated image generating unit 312 mayuse a cache for the overlapped part.

Next, the operation of the radar system of the third example embodimentwill be described with reference to the flowcharts of FIGS. 13A-13C.FIG. 13A shows the entire processing of the radar system. FIG. 13B andFIG. 13C show processes executed by the movement estimation unit 206.

The processing of steps S101, S102, and S203 is the same as theprocessing in the second example embodiment. The movement estimationunit 206 outputs the movement amount for each interest point and theposition of the interest point at the irradiation time of eachtransmission antenna 103 to the image area divider 311.

In this example embodiment, the movement amount estimation of the object800 based on the signal from the sensor 105 (signal that can identifythe position or velocity or image of the object 800) and the movementamount estimation based on the radar image are also alternativelyexecuted. When the radar device 301 is configured to perform themovement amount estimation based on the radar image, the radar signaltransmission and receiving unit 104 also outputs the radar signal andthe irradiation time of each transmission antenna to the movementestimation unit 206.

In the case where the radar device 301 is configured to perform themovement amount estimation based on the radar image, the movementestimation unit 206 does not execute the processing of step S102. In thecase where the radar device 301 is so configured, the sensor 105 neednot be installed as described above.

The image area divider 311 divides the image based on the positions ofthe interest points (step S301). The image area divider 311 outputs dataindicating areas in the image obtained by dividing and movement amountsof corresponding interest points to the motion-compensated imagegenerating unit 312.

The motion-compensated image generating unit 312 generates a radar imageof each divided area based on the radar signals input from the radarsignal transmission and receiving unit 104 and the movement amount ofeach interest point at an irradiation time of each transmission antenna102 output from the image area divider 311. Then, the motion-compensatedimage generating unit 312 generates the radar image by equation (9), forexample (step S304).

In this example embodiment, the radar device 301 estimates the movementof each interest point in the object 800 using information (position orvelocity information) or images obtained from the sensor 105, or radarimages. Then, the radar device 301 generates a final radar image bycompensating for the movements of the estimated interest points. As aresult, a radar image is obtained in which blurring caused by differentmovements of a plurality of positions in the object 800 is suppressed.In addition, even when the movements of the plurality of positions inthe object 800 are different, it is possible to obtain a single radarimage in which they are compensated simultaneously.

Example Embodiment 4

FIG. 14 is a block diagram showing a configuration example of the radarsystem of the fourth example embodiment. The radar system of the fourthexample embodiment includes a radar device 401, the transmission antenna102, and the receiving antenna 103. Although one transmission antenna102 and one receiving antenna 103 are illustrated in FIG. 14,practically, a large number of transmission antennas 102 and a largenumber of receiving antennas 103 are installed.

The radar device 401 includes a radar signal transmission and receivingunit 104, an image DB 107 that stores radar images and imaging times, animage generating unit 108 that generates a radar image based on theradar signals and stores the radar image and the imaging time in theimage DB 107, an image area divider 411, a movement amount estimationunit 410 that estimates a movement of an object based on images withdifferent imaging times, and a motion-compensated image generating unit412 that generates a radar image using the radar signals and themovement amount estimated for each area obtained by the division.

The transmission antenna 102, the receiving antenna 103, the radarsignal transmission and receiving unit 104, the image DB 107, and theimage generating unit 108 have the same functions as those of the thirdexample embodiment shown in FIG. 10.

The image area divider 411 obtains a radar image from the image DB 107and divides the radar image into areas. The image area divider 411outputs data indicating areas obtained by the division to the movementamount estimation unit 410. The image area divider 411 can use aclustering method such as the K-means method when dividing the radarimage into areas. For example, the image area divider 411 may divide theimage by making only the area around the pixel whose reflectionintensity (amplitude) of the radar image is equal to or greater than athreshold value and clustering such as the K-means method on the limitedarea. A method for dividing the image may be predetermined. In such acase, the image area divider 411 may divide the image into N_(z) equallyspaced areas in the z direction (depth direction relative to the radarplane), for example. The area obtained by dividing by clustering isdenoted by V_(p) as in the case of the third example embodiment.

The movement amount estimation unit 410 estimates the movement amount ofthe object 800 in each area based on data indicating the divided areainput to the image area divider 411. The movement amount estimation unit410 outputs the estimated movement amount to the motion-compensatedimage generating unit 412. The movement amount estimation unit 410 canestimate the movement amount for each area using any of the methods usedin the first to third example embodiments. The estimated movement amountfor each image area is denoted as Δ_(p)(t_(i)).

The motion-compensated image generating unit 412 operates as in thethird example embodiment.

Next, the operation of the radar system of the fourth example embodimentwill be described with reference to the flowchart of FIG. 15.

The radar signal transmission and receiving unit 104 performs a processsimilar to that in the third example embodiment (step S101). The imagegenerating unit 108 inputs the radar signals from the radar signaltransmission and receiving unit 104 and generates a radar image, similarto the third example embodiment (step S234). The image generating unit108 stores the generated radar image and the imaging time in the imageDB 107 (step S235), as in the third example embodiment.

The image area divider 411 divides the image (radar image) stored in theimage DB 107 into areas (step S401). The image area divider 411 outputsdata indicating areas obtained by the division to the movement amountestimation unit 410.

The movement amount estimation unit 410 estimates the movement amount ofthe object 800 for each area in the image (step S402). The movementamount estimation unit 410 outputs the estimated movement amount to themotion-compensated image generating unit 412.

The motion-compensated image generating unit 412 generates a radar imagesimilarly to the motion-compensated image generating unit 312, byequation (9), for example (step S304).

In this example embodiment, the radar device 401 estimates the movementof each interest point in the object 800 using the radar image. Then,the radar device 401 generates a final radar image by compensating forthe movements of the estimated interest points. As a result, a radarimage is obtained in which blurring caused by different movements of aplurality of positions in the object 800 is suppressed. In addition,even when the movements of the plurality of positions in the object 800are different, it is possible to obtain a single radar image in whichthey are compensated simultaneously.

The functions (processes) in each of the above example embodiments maybe realized by a computer having a processor such as a centralprocessing unit (CPU), a memory, etc. For example, a program forperforming the method (processing) in the above example embodiments maybe stored in a storage device (storage medium), and the functions may berealized with the CPU executing the program stored in the storagedevice.

FIG. 16 is a block diagram showing an example of a computer with a CPU.The computer is implemented in a radar device. The CPU 1000 executesprocessing in accordance with a program stored in a storage device 1001to realize the functions in the above example embodiments. That is, thecomputer realizes the functions of the radar signal transmission andreceiving unit 104, the image generating unit 108, the movement amountestimation unit 110, 210, 410, the motion-compensated image generatingunit 112, 212, 312, 412, the interest point extraction unit 209, and theimage area divider 311, 411 in the radar devices 101, 201, 301, and 401shown in FIGS. 1, 7, 10, and 14.

A graphics processing unit (GPU) may be used in place of or togetherwith the CPU 1000. In addition, some of the functions in the radardevices 101, 201, 301, and 401 shown in FIGS. 1, 7, 10, and 14 may berealized by the semiconductor integrated circuit, and other portions maybe realized by the CPU 1000 or the like.

The storage device 1001 is, for example, a non-transitory computerreadable medium. The non-transitory computer readable medium includesvarious types of tangible storage media. Specific examples of thenon-transitory computer readable medium include magnetic storage media(for example, flexible disk, magnetic tape, hard disk), magneto-opticalstorage media (for example, magneto-optical disc), compact disc-readonly memory (CD-ROM), compact disc-recordable (CD-R), compactdisc-rewritable (CD-R/W), and a semiconductor memory (for example, maskROM, programmable ROM (PROM), erasable PROM (EPROM), flash ROM).

The program may be stored in various types of transitory computerreadable media. The transitory computer readable medium is supplied withthe program through, for example, a wired or wireless communicationchannel, or, through electric signals, optical signals, orelectromagnetic waves.

The memory 1002 is a storage means implemented by a RAM (Random AccessMemory), for example, and temporarily stores data when the CPU 1000executes processing. It can be assumed that a program held in thestorage device 1001 or a temporary computer readable medium istransferred to the memory 1002 and the CPU 1000 executes processingbased on the program in the memory 1002.

The memory 1002 or the storage device 1001 realizes the image DB 107 ineach of the above example embodiments.

FIG. 17 is a block diagram showing the main part of the radar system.The radar system 11 shown in FIG. 17 comprises a plurality oftransmission antennas 12 (in the example embodiments, realized by thetransmission antenna 102) which irradiate electromagnetic waves, aplurality of receiving antennas 13 (in the example embodiments, realizedby the receiving antenna 103) which receive the irradiatedelectromagnetic waves that have been reflected and generatingmeasurement signals, radar signal transmission and receiving means 14(in the example embodiments, realized by the radar signal transmissionand receiving unit 104) for obtaining the measurement signals, movementestimation means 15 (in the example embodiments, realized by themovement estimation unit 106, 206) for estimating the movement of anobject, and motion-compensated image generation means 16 (in the exampleembodiments, realized by the motion-compensated image generating unit112, 212, 312, 412) for generating a radar image, based on themeasurement signals and the estimated object movement.

A part of or all of the above example embodiments may also be describedas, but not limited to, the following supplementary notes.

(Supplemental note 1) A radar system comprising:

a plurality of transmission antennas which irradiate electromagneticwaves,

a plurality of receiving antennas which receive the irradiatedelectromagnetic waves that have been reflected and generatingmeasurement signals,

radar signal transmission and receiving means for obtaining themeasurement signals,

movement estimation means for estimating a movement of an object, and

motion-compensated image generation means for generating a radar image,based on the measurement signals and the estimated movement of anobject.

(Supplemental note 2) The radar system according to Supplemental note 1,wherein

the movement estimation means includes movement amount estimation meansfor estimating the movement amount of the object at an irradiation timeof the electromagnetic wave of each transmission antenna, and

the motion-compensated image generation means generates the radar image,based on the estimated movement amount of the object.

(Supplemental note 3) The radar system according to Supplemental note 2,wherein

the movement amount estimation means estimates the movement amount ofthe object at the irradiation time of each transmission antenna, basedon images based on the measurement signals or images obtained from anexternal sensor with different imaging times.

(Supplemental note 4) The radar system according to Supplemental note 3,wherein

the movement amount estimation means obtains the movement amount of theobject from correlation among a plurality of images with differentimaging times, calculates movement velocity of the object based on theobtained movement amount and the difference of the imaging times, andestimates the movement amount of the object at the irradiation time ofeach transmission antenna from the calculated movement velocity.

(Supplemental note 5) The radar system according to Supplemental note 3,wherein

the movement amount estimation means estimates the movement amount ofthe object at the irradiation time of each transmission antenna, basedon a plurality of images with different imaging times, wherein theimages are based on the measurement signals obtained by combinations ofthe transmission antenna and the receiving antenna whose centerpositions of antenna apertures formed by the transmission antenna andthe receiving antenna are the same or close.

(Supplemental note 6) The radar system according to any one ofSupplemental notes 1 to 5, further comprising:

interest point extraction means for extracting one or more interestpoints in the object, wherein

the motion-compensated image generation means generates the radar image,based on the movement of the object for each interest point at theirradiation time of each transmission antenna.

(Supplemental note 7) The radar system according to Supplemental note 6,wherein

the interest point extraction means extracts interest points in theobject from the image based on the measurement signals or an imageobtained from an external sensor, and

the movement estimation means estimates the movement amount for each ofthe interest points at the irradiation time of each transmissionantenna.

(Supplemental note 8) The radar system according to any one ofSupplemental notes 1 to 7, further comprising:

image area division means for dividing the image, based on the interestpoints in the object, wherein

the motion-compensated image generation means generates the radar image,based on the movement of the interest point in each area obtained by thedivision.

(Supplemental note 9) The radar system according to Supplemental note 8,wherein

the image area division means divides the image so that a distancebetween the interest point and an imaging position is minimized.

(Supplemental note 10) The radar system according to any one ofSupplemental notes 1 to 5, further comprising:

image area division means for dividing the image based on themeasurement signals,

wherein

the movement estimation means estimates the movement of the object foreach area obtained by the division, and

the motion-compensated image generation means generates the radar image,based on the movement of the object in each area obtained by division.

(Supplemental note 11) The radar system according to Supplemental note10, wherein

the image area division means divides the image by clustering in thedepth direction to the radar plane.

(Supplemental note 12) The radar system according to any one ofSupplemental notes 1 to 11, wherein

the movement estimation means estimates the movement of the object,based on a position or velocity of the object obtained from an externalsensor.

(Supplemental note 13) An imaging method comprising:

obtaining the measurement signals based on reflected waves ofelectromagnetic waves irradiated from a plurality of transmissionantennas,

estimating a movement of an object, and

generating a radar image, based on the measurement signals and theestimated object movement.

(Supplemental note 14) The imaging method according to Supplemental note13, further comprising

estimating the movement amount of the object at the irradiation time ofthe electromagnetic wave of each transmission antenna, and

generating the radar image, based on the estimated movement amount ofthe object.

(Supplemental note 15) The imaging method according to Supplemental note14, wherein

the movement amount of the object at the irradiation time of eachtransmission antenna is estimated, based on images based on themeasurement signals or images obtained from an external sensor withdifferent imaging times.

(Supplemental note 16) An imaging program causing a computer to execute:

a process of obtaining the measurement signals based on reflected wavesof electromagnetic waves irradiated from a plurality of transmissionantennas,

a process of estimating a movement of an object, and

a process of generating a radar image based on the measurement signalsand the estimated object movement.

(Supplemental note 17) The imaging program according to Supplementalnote 16, causing the computer to further execute

a process of estimating the movement amount of the object at theirradiation time of the electromagnetic wave of each transmissionantenna, and

a process of generating the radar image based on the estimated movementamount of the object.

(Supplemental note 18) The imaging program according to Supplementalnote 17, wherein

the movement amount of the object at the irradiation time of eachtransmission antenna is estimated, based on images based on themeasurement signals or images obtained from an external sensor withdifferent imaging times.

Although the invention of the present application has been describedabove with reference to example embodiments, the present invention isnot limited to the above example embodiments. Various changes can bemade to the configuration and details of the present invention that canbe understood by those skilled in the art within the scope of thepresent invention.

REFERENCE SIGNS LIST

11 Radar system

12 Transmission antenna

13 Receiving antenna

14 Radar signal transmission and receiving means

15 Movement estimation means

16 Motion-compensated image generation means

101, 201, 301, 401 Radar device

102 Transmission antenna

103 Receiving antenna

104 Radar signal transmission and receiving unit

105 Sensor (external sensor)

106, 206 Movement estimation unit

107 Image DB (image database)

108 Image generating unit

110, 210, 410 Movement amount estimation unit

112, 212, 312, 412 Motion-compensated image generating unit

209 Interest point extraction unit

311, 411 Image area divider

1000 CPU

1001 Storage device

1002 Memory

What is claimed is:
 1. A radar system comprising: a plurality of transmission antennas which irradiate electromagnetic waves, a plurality of receiving antennas which receive the irradiated electromagnetic waves that have been reflected and generating measurement signals, a radar signal transmission and receiving unit which obtains the measurement signals, a movement estimation unit which estimates a movement of an object, and a motion-compensated image generation unit which generates a radar image, based on the measurement signals and the estimated movement of an object.
 2. The radar system according to claim 1, wherein the movement estimation unit includes a movement amount estimation unit which estimates the movement amount of the object at an irradiation time of the electromagnetic wave of each transmission antenna, and the motion-compensated image generation unit generates the radar image, based on the estimated movement amount of the object.
 3. The radar system according to claim 2, wherein the movement amount estimation unit estimates the movement amount of the object at the irradiation time of each transmission antenna, based on images based on the measurement signals or images obtained from an external sensor with different imaging times.
 4. The radar system according to claim 3, wherein the movement amount estimation unit obtains the movement amount of the object from correlation among a plurality of images with different imaging times, calculates movement velocity of the object based on the obtained movement amount and the difference of the imaging times, and estimates the movement amount of the object at the irradiation time of each transmission antenna from the calculated movement velocity.
 5. The radar system according to claim 3, wherein the movement amount estimation unit estimates the movement amount of the object at the irradiation time of each transmission antenna, based on a plurality of images with different imaging times, wherein the images are based on the measurement signals obtained by combinations of the transmission antenna and the receiving antenna whose center positions of antenna apertures formed by the transmission antenna and the receiving antenna are the same or close.
 6. The radar system according to claim 1, further comprising: an interest point extraction unit which extracts one or more interest points in the object, wherein the motion-compensated image generation unit generates the radar image, based on the movement of the object for each interest point at the irradiation time of each transmission antenna.
 7. The radar system according to claim 6, wherein the interest point extraction unit extracts interest points in the object from the image based on the measurement signals or an image obtained from an external sensor, and the movement estimation unit estimates the movement amount for each of the interest points at the irradiation time of each transmission antenna.
 8. The radar system according to claim 6, further comprising: an image area division unit which divides the image, based on the interest points in the object, wherein the motion-compensated image generation unit generates the radar image, based on the movement of the interest point in each area obtained by the division.
 9. The radar system according to claim 8, wherein the image area division unit divides the image so that a distance between the interest point and an imaging position is minimized.
 10. The radar system according to claim 1, further comprising: an image area division unit which divides the image based on the measurement signals, wherein the movement estimation unit estimates the movement of the object for each area obtained by the division, and the motion-compensated image generation unit generates the radar image, based on the movement of the object in each area obtained by division.
 11. The radar system according to claim 10, wherein the image area division unit divides the image by clustering in the depth direction to the radar plane.
 12. The radar system according to claim 1, wherein the movement estimation unit estimates the movement of the object, based on a position or velocity of the object obtained from an external sensor.
 13. An imaging method comprising: obtaining the measurement signals based on reflected waves of electromagnetic waves irradiated from a plurality of transmission antennas, estimating a movement of an object, and generating a radar image, based on the measurement signals and the estimated object movement.
 14. The imaging method according to claim 13, further comprising estimating the movement amount of the object at the irradiation time of the electromagnetic wave of each transmission antenna, and generating the radar image, based on the estimated movement amount of the object.
 15. The imaging method according to claim 14, wherein the movement amount of the object at the irradiation time of each transmission antenna is estimated, based on images based on the measurement signals or images obtained from an external sensor with different imaging times.
 16. A non-transitory computer readable information recording medium storing an imaging program causing a computer to execute: obtaining the measurement signals based on reflected waves of electromagnetic waves irradiated from a plurality of transmission antennas, estimating a movement of an object, and generating a radar image based on the measurement signals and the estimated object movement.
 17. The information recording medium according to claim 16, wherein the imaging program causes the computer to further execute estimating the movement amount of the object at the irradiation time of the electromagnetic wave of each transmission antenna, and generating the radar image based on the estimated movement amount of the object.
 18. The information recording medium according to claim 17, wherein the movement amount of the object at the irradiation time of each transmission antenna is estimated, based on images based on the measurement signals or images obtained from an external sensor with different imaging times. 